Exoplanets can now be discovered using chemistry!

Forming exoplanets alter the chemical composition of protoplanetary disks so much that their presence can be detected indirectly, according to observations made with ESO’s radio telescope network.

famous Encyclopedia of extrasolar planetsAnd Founded in 1995 by Jean Schneider at the Paris Observatory, it presents in this month of June 2023 more than 5,400 outer planetsouter planets Among those whose existence has been confirmed, after being spotted by satellites such as Kepler and TESS. It is in this last state of the planets that the slight fall of the brightnessbrightness which they provoke by passing in front of them sunsun for ground observers.

more than three TransitTransit There is a need to start making sure that an exoplanet is seen indirectly and not just a natural variation in brightness a stara star Part of a big family variable starsvariable stars monitor it Astronomy scientistsAstronomy scientists Hobby.

Another monitoring technique, which also serves to confirm the detections made by traversal, is the technique gearsgears Radial and can be put into action on the ground using telescopestelescopes that measureDoppler effectDoppler effect produced on a lighta light I star it a movementa movement It is the oscillation that periodically brings this star closer and farther from us. This motion is a reflection of the exoplanet’s gravitational pull orbitorbit. We can also sometimes image an exoplanet directly in orbit around its host star. For more details on these methods of observation, see CEA videos on exoplanets like the one below.

In 1995, the discovery of an exoplanet, a planet orbiting another sun, opened up the dream of other worlds to the entire universe. How many habitable or even inhabited planets are there in our galaxy: billions or just one? New observational techniques from space improve sensitivity. With the Kepler Space Telescope, the number of exoplanets is exploding. In 2018, there were nearly 4,000. Explore the exoplanets with our web series in nine episodes. A video is found every week on our YouTube channel. Playlist proposed by CEA and the University of Paris-Saclay as part of the European research project H2020 Exoplanets-A. © CEA Research

Initial star from the Henry Draper catalog

I’AstrophysicistAstrophysicist Charles Lowthe Center for Astrophysics | Harvard and Smithsonian, In the United States, he is the co-author with colleagues of an article in language Astrophysical Journal Letters which can be found for free at arXiv. He is now reporting a new indirect method for detecting the presence of an exoplanet. This time, it’s not just about physics but about chemistrychemistry. It has been put into practice withThe Atacama group is millimeter/meter large (ALMA) to study the disk of protoplanets around their young protstarprotstarHD 169142, located at constellationconstellation from arch to 374 light yearslight years we’ve got solar systemsolar system.

Did you know ?

The Henry Draper Catalog (HD) collects data on more than 225,000 stars with apparent magnitudes of about 9. Created at the beginning of XXH century by astronomer Annie Jump Cannon and her colleagues Harvard College ObservatoryIt covers almost the entire celestial vault. It takes its name from the pioneer of astrophotography, who was the first to obtain a stellar spectrum, Vega’s spectrum, in 1872. When he died, his widow funded the production of this catalog, which was later used extensively by astronomers. This is why many of the Milky Way’s stars studied for their exoplanets are denoted by the letters HD.

In fact, exoplanets have been suspected in this protoplanetary disk for several years now Scientists from the University of Liege and Monash University I think they’ve already there recently discovered a giant protoplanet similar to JupiterJupiter : HD 169142 .

In a press release from National radioradio Astronomy Observatory (NRAO), Charles Low explains: “ When we examined HD 169142 and its disks at sub-millimeter wavelengths, we identified several compelling chemical signals for this protoplanet. gas giantgas giant recently confirmed. We now have evidence that we can use chemical signatures to identify the types of planets that might be forming in the disks around young stars. »

In addition to particlesparticles to Carbon MonoxideCarbon Monoxide He wears isotopesisotopes Carbon 12 and 13 (both 12Carbon monoxide and sound isotopesisotopes 13CO) and carbon monoxide matchsticksmatchsticks (SO), astrophysicists highlighted spectral linesspectral lines The ID card is formed from monosulfide siliconsilicon SiS.

Shock waves that vaporize dust

Charles Lu explains on this subject that SiS was a molecule not seen before in a protoplanetary disk, let alone near a giant protoplanet. revealing ofproblemproblem SiS appeared to us because it meant that this protoplanet must have produced powerful shock waves in the surrounding gas “.

Obviously, this detectable molecule must come from grains of silicate dust that are being heated by massive shock waves. These shock waves must be analogues waveswaves The bow that forms in the front of a boat when it cuts through the water as it moves forward. It is not difficult to infer that in the case of HD 169142, the waves from an exoplanet must be drilling a hole in the protoplanetary disk by moving within it and attracting material accreting on it.

It is also clear that this chemical signature must be usable in another state Protoplanetary disksProtoplanetary disks In which we have not yet eliminated any candidate for the title of exoplanet.

There is great diversity in exoplanets and using the chemical signatures observed with ALMA gives us a new way to understand how different protoplanets grew over time and ultimately relate their properties to those of exoplanet systems. In addition to providing a new tool for searching for planets with ALMA, this discovery opens the way for WindowWindow Lots of exciting chemistry that we’ve never seen before. As we continue to explore more and more disks around young stars, we will inevitably find other interesting yet unexpected particles, just like SiS. Results like these suggest we’re only scratching the surface of the true chemical diversity associated with protoplanetary settings. Charles Low concludes.

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